In Phase 1 of this project, the Contractor developed a 3D co-culture of iPS hepatocytes with non-parenchymal liver cells in the high-throughput HepaPlate model which mimics the structure of the liver sinusoid. The culture of iPS hepatocytes in the HepaPlate demonstrated improved biological function and markers of differentiation in vitro. A panel of multiplexed HTS/HCS assays in the HepaPlate were also developed to measure multiple mechanisms of hepatocyte toxicity and maturation. In Phase II of this project, the Contractor will optimize the composition of an iPS hepatocyte-based 3D co-culture model in the OrganoPlate (the HepaPlate iPS) that was developed in Phase I to improve iPS hepatocyte maturation. The capacity of the HepaPlate iPS will be determined to provide a reproducible and robust multiparameter readouts of toxicity, and to facilitate high-throughput screening and detect compound toxicity. Once executed these studies will establish the HepaPlate iPS as a high-throughput screening platform for assessment of pharmaceutical and environmental hepatotoxicity. When implemented early in drug discovery, drug companies will be able to prioritize drug candidates based on efficacy and toxicity which will allow for prioritization of candidates more likely to be successful in human clinical trials.